Hubble captures sharpest view yet of interstellar comet 3I/ATLAS
The Hubble Space Telescope has delivered the clearest image so far of 3I/ATLAS, a high‑speed visitor from another star system now passing through our solar neighborhood. NASA and the European Space Agency released the latest images on Thursday, showing a teardrop-shaped cloud of dust surrounding the comet’s nucleus and faint traces of a dusty tail. When Hubble photographed it on July 21, 2025, the object was about 277 million miles from Earth and on a trajectory that will take it closer to Mars than to our planet, posing no threat.
First identified last month by a telescope in Chile, 3I/ATLAS is only the third confirmed interstellar object ever observed in our solar system, following 1I/‘Oumuamua in 2017 and 2I/Borisov in 2019. New analysis published in Astrophysical Journal Letters uses Hubble’s data to refine the size of its icy core to no larger than 3.5 miles across—and it could be as small as roughly 1,000 feet—highlighting how difficult it is to isolate a comet’s nucleus from the surrounding dust and gas.
The comet is racing inward at about 130,000 mph. It is expected to make its closest approach to the sun in late October, passing between the orbits of Mars and Earth. According to NASA, it should remain visible to telescopes through September before becoming too near the sun’s glare to observe, then reappearing on the far side of the sun by early December for renewed study.
Las Cumbres Observatory notes that these rare interstellar visitors tend to be very dark and reddish, reflecting only about 5% of the sunlight that hits them—akin to the reflectivity of asphalt. Unlike ‘Oumuamua, 3I/ATLAS shows little change in brightness as it rotates, suggesting a more spherical shape.
As observations ramp up, some scientists are posing provocative questions. Harvard astrophysicist Avi Loeb has suggested the object might be technological in origin and urged intensive monitoring for any unusual behavior. His view remains speculative, and Hubble’s detection of a dust coma and a tail is consistent with a natural comet. Researchers broadly agree the best course is to gather as much data as possible while the object is accessible.
Why the size estimates span so widely
– A comet’s nucleus is typically hidden by a bright, diffuse envelope of dust and gas (the coma). Telescopes measure the coma’s brightness and shape, then model how much of that light could be coming from the solid core.
– Different assumptions about dust production and grain size yield different limits, so early size estimates often tighten as higher-resolution data arrive—exactly what Hubble is now providing.
What to watch next
– Activity: Changes in the dust coma and tail as 3I/ATLAS warms near the sun will help reveal its composition and how its surface behaves.
– Shape and rotation: Continued photometry can test the early indication that it’s relatively spherical and not strongly elongated.
– Chemistry: Spectra obtained when it reemerges in December could show which ices are driving its activity and how it compares with comets formed around other stars.
The bigger picture
Each interstellar object offers a rare sample of material forged in another planetary system. With only two prior examples on record, 3I/ATLAS is a welcome chance to test what’s common—and what’s exotic—about the building blocks of planets beyond our sun. Hubble’s crisp view underscores how much can still be learned with careful, sustained observation.
Summary
– Hubble’s latest images show 3I/ATLAS with a dust coma and faint tail at a distance of 277 million miles.
– The interstellar comet’s nucleus is now constrained to no more than 3.5 miles across and could be as small as about 1,000 feet.
– It will pass safely through the inner solar system, closer to Mars than Earth, reaching closest approach to the sun in late October.
– Visible to telescopes through September, it should reappear for study in early December after passing behind the sun.
– Early indicators suggest a dark, reddish, low-reflectivity surface and a likely more spherical shape than ‘Oumuamua.
Positive outlook
This is a rare, low-risk, high-reward event: a safely passing interstellar visitor that astronomers can track for months. With multiple observatories engaged and Hubble already refining key details, 3I/ATLAS promises new clues about how other star systems form comets—and, by extension, planets.